As shown in FIG. 1 ,a prior art tricycle "A" is intended for a child and is made up of a body frame by welding. The tricycle "A" has a handlebar A1 which is connected with a rear frame A2 by a support frame A3 the rear frame A2 is composed of a tubular frame A21 which is provided with an insertion seat A22 for mounting a holding frame A4. Such a prior art tricycle as described above is disadvantageous in design in is rather complicated in construction, and lacks an auxiliary steering device enabling an adult to teach a child to ride the tricycle with ease and without back pain.